Processes for forming detergent granules are well known in the art and have typically involved the steps of forming a detergent slurry by mixing a builder, a neutralized or acid-form anionic surfactant, a filler, water/free moisture, processing aids, deaerants, brighteners and/or organic polymers in a crutcher, pumping the detergent slurry to the top of a spray drying tower, and spraying the detergent slurry from nozzles in the tower to form atomized droplets. Hot air is pumped into the bottom of the spray drying towers such that when the atomized droplets are sprayed into the hot air, they immediately dry into a powder as the free moisture evaporates. The spray-dried granules thus formed are then collected at the bottom of the tower. Alternatively, agglomeration process are also well known.
While the spray drying conditions within the spray drying tower contain many critical variables such as temperature, air flow rate, humidity, etc., the conventional spray drying wisdom leads one to believe that adding high levels of anionic and cationic surfactants, especially anionic surfactants to the slurry prior to pumping and spray drying is highly desirable in order to result in a proper slurry. Without such a proper slurry, having the right phase, viscosity and pumping characteristics, the resulting particles will be too light, too dense, too wet, the wrong size, and/or sticky, leading to over hydration and thickening of the slurry, lumps and/or possess other undesirable physical characteristics. Thus, the detergent slurries employed in typical spray drying processes contain from about 15% to about 25% organic materials, which correspond to from 20% to 40% organic materials in the final spray-dried granule. These organic materials are typically anionic and cationic surfactants, polymers, etc. However, it has been found that high levels of surfactants in the spray dried granule can limit the amount and type of other additives added, and can also limit the feasibility of additional processing. For example, adding even up to 3% nonionic surfactant to spray dried granules containing these levels of organic materials often results in sticky granules which have poor flow properties, and excessive caking. Also, spray dried granules containing anionic surfactants may not have a sufficient porosity to absorb large amounts of other additives during subsequent processing. In addition, spray dried granules containing anionic surfactants may reduce formulation alternatives, as builders such as phosphate and zeolites are required because of their strong binding abilities to hard metal ions. Furthermore, such builders have certain environmental and cost limitations. Thus, while spray drying processes are known, and have been for many years, it has now been recognized that they are relatively inflexible and possess significant processing constraints. In addition, certain process are only adequate for forming a high density and/or a compact detergent granule, whereas certain markets and consumers prefer low density granules.
While some detergent granule processes and detergent granules are known, it has been found that such detergent granules typically possess limitations in, for example, production rates, density, and/or solubility, caking etc.
Accordingly, the need exists for a more process for forming a low density, i.e., from about 300 g/L to about 600 g/L, detergent granule which overcomes the above limitations and problems, while reducing the need for significant capital investment.